In the recent past immense research has been dedicated to the discovery and understanding of the structure and functions of enzymes and bio-molecules associated with various diseases. One such important class of enzymes that has been the subject of extensive research is Protein Kinase.
In general, protein kinases represent a set of structurally related pbosphoryl transferases, having conserved structures and catalytic functions. These enzymes modify proteins by chemically adding phosphate groups (phosphorylation). Phosphorylation involves the removal of a phosphate group from ATP and covalently attaching it to amino acids that have a free hydroxyl group such as serine, threonine or tyrosine. Phosphorylation usually results in a functional change of the target protein (substrate) by altering enzyme activity, cellular localization or association with other proteins. Up to 30% of all proteins may be modified by kinase activity.
This class of proteins are classified into subsets depending upon the substrate they act upon such as tyrosine kinase, serine/theronine kinase, histidine kinase and the like. These proteins can also be classified based on their localization into receptor tyrosine kinases (RTKs) or non-receptor tyrosine kinases.
Receptor tyrosine kinases (RTKs) have an extracellular portion, a transmembrane domain, and an intracellular portion, while non-receptor tyrosine kinases are entirely intracellular. Receptor tyrosine kinase mediated signal transduction is typically initialed by an extracellular interaction with a specific growth factor (ligand), followed by receptor dimerization, stimulation of the intrinsic protein tyrosine kinase activity, and phosphorylation of amino acid residues. The ensuing conformational change leads to the formation of complexes with a spectrum of cytoplasmic signalling molecules and facilitates a myriad of responses such as cell division, differentiation, metabolic effects, and changes in the extracellular microenvironment.
At present, at least twenty (20) distinct RTK subfamilies have been identified. One subfamily of the RTKs is designated as the Met subfamily (c-Met, Ron and Sea). For a detailed discussion of protein kinases, see, Plowman et al., DN&P 7(6): 334-339, 1994, Blume-Jensen, P. et al, Nature 2001, 411(6835):355-365 and Manning, G. et al., Science. 2002, 298(5600): 1912-1934.
Kinases have also been classified either based on the pathway or the diseases in which they are involved (visit:www.reactionbiology.com/pages/kinase.htm), c-Met has been identified as involved in oncogenesis.
Protein kinases exert their physiological functions through phosphorylation of proteins (or substrates) thereby modulating the cellular activities of the substrate in various biological contexts. Protein kinases are known to control a wide variety of biological processes such as cell growth, survival and differentiation, organ formation and morphogenesis, neovascularization, tissue repair and regeneration. In addition to their functions in normal tissues/organs, many protein kinases also play specialized roles in a host of human diseases including cancer. A subset of protein kinases (also referred to as oncogenic protein kinases), when dysregulated, can cause tumor formation and growth and contribute to tumor maintenance and progression (Blume-Jensen P et al. Nature 2001, 411(6835):355-365). Thus far, oncogenic protein kinases represent one of the largest and most attractive groups of protein targets for therapeutic intervention and drug development.
Both receptor and non-receptor protein kinases have been found to be attractive targets for small molecule drug discovery due to their impact on cell physiology and signalling. Dysregulation of protein kinase activity thus leads to altered cellular responses including uncontrolled cell growth associated with cancer. In addition to oncological indications, altered kinase signalling is implicated in numerous other pathological diseases. These include, but are not limited to immunological disorders, cardiovascular diseases, inflammatory diseases, and degenerative diseases.
A significant number of tyrosine kinases (both receptor and nonreceptor) are associated with cancer (see Madhusudan S, Ganesan T S. Tyrosine kinase inhibitors in cancer therapy. Clin. Biochem. 2004. 37(7):618-35.). Clinical studies suggest that over expression or dysregulation of tyrosine kinases may also be of prognostic value. For example, members of the HER family of RTKs have been implicated in breast, colorectal, head and neck and lung cancer. Mutation of c-Kit tyrosine kinase is associated with decreased survival in gastrointestinal stromal tumors (GIST). In acute myelogenous leukemia, Flt-3 mutation predicts shorter disease free survival. VEGFR expression, which is important for tumor angiogenesis, is associated with a lower survival rate in lung cancer. Tie-1 kinase expression is inversely correlated to survival in gastric cancer, BCR-AbI expression is an important predictor of response in chronic myelogenous leukemia while Src tyrosine kinase expression is co-related to the stage of colorectal cancer.
Modulation (particularly inhibition) of cell proliferation and angiogenesis, the two key cellular processes needed for tumor growth and survival is an attractive goal for development of small-molecule drugs (Matter A. Drug Disc Technol 2001, 6, 1005-1024). Anti-angiogenic therapy represents a potentially important approach for the treatment of solid tumors and other diseases associated with dysregulated vascularisation including ischemic coronary artery disease, diabetic retinopathy, psoriasis and rheumatoid arthritis. Similarly, cell antiproliferative agents are desirable to slow or inhibit the growth of tumors.
Some of the kinases implicated in cancer are c-Met, RON (recepteur d'origine nantais) receptor, Vascular Endothelial Growth Factor (VEGF) receptor, Epidermal growth factor receptor kinase (EGF-R kinase), Eph receptors, c-Kit, and Flt-3.
A number of small molecule kinase modulators have found their way into the clinic which either act selectively on either one or multiple kinases. These include Gefitinib (AstraZeneca), a EGFR kinase inhibitor; Gleevec (Novartis), a dual c-Kit and Abl kinase inhibitor approved for the treatment of Chronic Myeloid Leukemia (CML) and gastrointestinal stroma cancers; Dasatinib (BMS), a dual BCR/ABL and Src family tyrosine kinases inhibitor, and Sunitinib (Pfizer) a multi kinase inhibitor targeting PDGF-R, VEGF-R, RET, KIT(CD117), CSF-1R and flt-3.
The kinase, c-Met, is the prototypic member of a subfamily of heterodimeric receptor tyrosine kinases (RTKs) which include Met, Ron and Sea (see Birchmeier, C. et al., Nat. Rev. Mol. Cell Biol. 2003, 4(12):915-925; Christensen, J. G. et al. Cancer Lett. 2005, 225(1): 1-26). Expression of c-Met occurs in a wide variety of cell types including epithelial, endothelial and mesenchymal cells where activation of the receptor induces cell migration, invasion, proliferation and other biological activities associated with “invasive cell growth.” As such, signal transduction through c-Met receptor activation is responsible for many of the characteristics of tumor cells.
The only high affinity endogenous ligand for c-Met is the hepatocyte growth factor (HGF), also known as scatter factor (SF). Binding of HGF to c-Met induces activation of the receptor via autophosphorylation resulting in an increase of receptor dependent signalling, which promotes cell growth and invasion. Both c-Met and HGF are widely expressed in a variety of organs, but their expression is normally confined to cells of epithelial and mesenchymal origin. Anti-HGF antibodies or HGF antagonists have been shown to inhibit tumor metastasis in vivo (See: Maulik et al Cytokine & Growth Factor Reviews 2002, 13, 41-59). The biological functions of c-Met (or c-Met signalling pathway) in normal tissues and human malignancies such as cancer have been well documented (Christensen, J. G. et al., Cancer Lett. 2005, 225(1): 1-26; Corso, S. et al., Trends in Mol. Med. 2005, 11 (6):284-292).
Tumor growth progression involves the recruitment of new blood vessels into the tumor as well as invasion, adhesion and proliferation of malignant cells. c-Met over expression has been demonstrated on a wide variety of tumor types including breast, colon, renal, lung, squamous cell myeloid leukemia, hemangiomas, melanomas, astrocytomas, and glioblastomas. Additionally activating mutations in the kinase domain of c-Met have been identified in hereditary and sporadic renal papilloma and squamous cell carcinoma. See Maulik et al Cytokine & growth Factor reviews 2002, 13, 41-59; Longati et al Curr Drug Targets 2001, 2, 41-55; Funakoshi et al Clinica Chimica Acta 2003 1-23. Thus modulation of c-Met offers an attractive opportunity to target key oncogenic processes thus limiting cell proliferation, survival and metastasis.
Dysregulated c-Met pathway is linked to tumor formation, growth, maintenance and progression (Birchmeier, C. et al., Nat. Rev. Mol. Cell. Biol, 2003, 4(12):915-925; Boccaccio, C. et al., Nat. Rev. Cancer 2006, 6(8):637-645; Christensen, J. G. et al., Cancer Lett. 2005, 225(1): 1-26). HGF and/or c-Met are over expressed in significant portions of most human cancers, and are often associated with poor clinical outcomes such as more aggressive disease, disease progression, tumor metastasis and shortened patient survival. Further, patients with high levels of HGF/c-Met proteins are more resistant to chemotherapy and radiotherapy. In addition to abnormal HGF/c-Met expression, the c-Met receptor can also be activated in cancer patients through genetic mutations (both germline and somatic) and gene amplification. Although gene amplification and mutations are the most common genetic alterations that have been reported in patients, the receptor can also be activated by deletions, truncations, and gene rearrangement, as well as abnormal receptor processing and defective negative regulatory mechanisms.
The various cancers in which c-Met is implicated include but are not limited to carcinomas (e.g., bladder, breast, cervical, cholangiocarcinoma, colorectal, esophageal, gastric, head and neck, kidney, liver, lung, nasopharyngeal, ovarian, pancreas, prostate, thyroid); musculoskeletal sarcomas (e.g., osteosarcaoma, synovial sarcoma, rhabdomyosarcoma); soft tissue sarcomas (e.g., MFH/fibrosarcoma, leiomyosarcoma, Kaposi's sarcoma); hematopoietic malignancies (e.g., multiple myeloma, lymphomas, adult T cell leukemia, acute myelogenous leukemia, chronic myeloid leukemia); and other neoplasms (e.g., glioblastomas, astrocytomas, melanoma, mesothelioma and Wilm's tumor (www.vai.org/met/; Christensen, J. G, et al., Cancer Lett. 2005, 225(1): 1-26). c-Met inhibitors may also be useful in preventative and adjuvant therapy settings. In addition, certain cancers (e.g., papillary renal cell carcinoma, and some gastric and lung cancers) may be treated with c-Met inhibitors as they are believed to be driven by c-Met mutation/genetic alteration and dependent on c-Met for growth and survival. These cancers are expected to be sensitive to treatment.
The notion that activated c-Met contributes to tumor formation and progression and could therefore be a potential target for effective cancer intervention has been further validated by numerous preclinical studies (Birchmeier, C. et al., Nat. Rev. Mol. Cell Biol. 2003, 4(12):915-925; Christensen, J. G. et al. Cancer Lett. 2005, 225(1): 1-26; Corso, S. et al., Trends in Mol. Med. 2005, 11(6):284-292). For example, studies have demonstrated that the tpr-met fusion gene, over expression of c-Met, and activated c-Met mutations caused oncogenic transformation of various model cell lines and resulted in tumor formation and metastasis in mice. Conversely, significant anti-tumor and anti-metastasis activities have been demonstrated in vitro and in vivo with agents that specifically impair and/or block HGF/c-Met signalling. Those agents include anti-HGF and anti-c-Met antibodies, HGF peptide antagonists, decoy c-Met receptor, c-Met peptide antagonists, dominant negative c-Met mutations, c-Met specific antisense oligonucleotides and ribozymes, and selective small molecule c-Met kinase inhibitors (Christensen, J. G. et al. Cancer Lett. 2005, 225(1): 1-26). In addition to its established role in cancer, abnormal HGF/c-Met signalling is also implicated in atherosclerosis, lung fibrosis, renal fibrosis and regeneration, liver diseases, allergic disorders, inflammatory and autoimmune disorders, cerebrovascular diseases, cardiovascular diseases, and conditions associated with organ transplantation. See Ma, H. et al., Atherosclerosis. 2002, 164(1):79-87; Crestani, B. et al., Lab. Invest. 2002, 82(8): 1015-1022; Sequra-Flores, A. A. et al. Rev. Gastroenterol. Mex. 2004, 69(4)243-250; Morishita, R. et al., Curr. Gene Ther, 2004, 4(2)199-206; Morishita, R. et al., Endocr. J. 2002, 49(3)273-284; Liu, Y., Curr, Opin. Nephrol. Hypertens. 2002, 11 (1):23-30; Matsumoto, K. et al., Kidney Int. 2001, 59(6):2023-2038; Balkovetz, D. F. et al., Int. Rev. Cytol. 1999, 186:225-250; Miyazawa, et al., J. Cereb. Blood Flow Metab. 1998, 18(4)345-348; Koch, A. F. et al., Arthritis Rheum. 1996, 39(9): 1566-1575; Futamatsu, H. et al., Circ. Res. 2005, 96(8)823-830; Eguchi, S, et al., Clin. Transplant. 1999, 13(6)536-544.
c-Met is thus an attractive target from a clinical perspective mainly because of its upstream localisation which aids in early detection and limiting metastasis and implications in the growth and metastases of most types of cancers. These observations suggest that c-Met kinase inhibitors would be an effective treatment for tumors driven by c-Met, and also would prevent disseminated micrometastases from further progression.
A family of novel compounds have been discovered which exhibit c-Met modulating ability and have an ameliorating effect against disorders related to abnormal c-Met activity such as Johnson & Johnson's JNJ-38877605, Amgen's AMG-458, Eisai's E-7050 and Pfizer's PF-04217903. However, to date, none of them have been used in a clinical study.

More recently Dussault et. al., Anti-Cancer Agents in Medicinal Chemistry, 2009, 9(2), 221-229, have provided additional insight about a receptor tyrosine kinase namely, RON (recepteur d'origine nantais) which is closely related to c-Met. Both c-MET and RON receptors upon activation can induce cell migration, invasion, proliferation and survival. Moreover, both possess oncogenic activity in vitro and in vivo and are often dysregulated in human cancers.
While c-Met is now a well-accepted target for anti-cancer treatment, less is known about the role of RON in cancer. Despite their common attributes, c-Met and RON are activated by different mechanisms in cancer cells. Due to a significant homology between the two RTKs, some small molecule kinase inhibitors of c-Met have inhibitory activity on RON suggesting that both receptors might be involved in cancer progression. The review (Dussault et al., supra) discusses the relevance of both c-Met and RON deregulation in human cancers and the progress made in identifying small molecule kinase inhibitors that can block the activity of these targets in vitro and in animal models. One of the compounds discussed in the review, AMG-458, inhibited c-Met and RON with IC50s of 4 and 9 nM respectively.
Various research groups around the world such as Amgen, Arquel, AstraZeneca, Bristol-Myers Squibb, Exelixis, Eisai, Incyte, MethylGene, Pfizer, SGX Pharma, SmithKline Beecham, Sobering, Vertex, Xcovery. Novartis and others have been working on targeting either single, dual or multiple kinase targets.
Patent literature belonging to some of these applicants include the following patents and/or patent applications: U.S. Pat. No. 7,446,199; U.S. Pat. No. 7,470,693; U.S. Pat. No. 7,459,562; U.S. Pat. No. 7,439,246; U.S. Pat. No. 7,432,373; U.S. Pat. No. 7,348,325; U.S. Pat. No. 7,173,031; U.S. Pat. No. 7,314,885; U.S. Pat. No. 7,169,800; US20100105656, US20090012076; US20080312232; US20080161305; US20070244116; US20070225307; US20070054928; US20070179130; US20070254868; US20070191369; US20060173055; US20060135537; US20050148574; US20050137201; US20050101650; WO2009002806; WO2008088881; WO2008051805; WO2008102870; WO2008078085; WO2008060866; WO200854702; WO2008036272; WO2007111904; WO2007064797; WO2006052913; WO2006021881; WO2006021886; WO2006021884; WO2006108059; WO006014325; WO2006052913; WO200507891; WO2005030140; WO2005040345; WO2005028475; WO2005016920.
Recent PCT patent applications viz., WO2009058728, WO2009058729, WO2009058730 and WO2009058739 all assigned to Schering corporation disclose a series of thiazole carboxamide compounds as protein kinase inhibitors and more specifically to be inhibiting Aurora, MEK1 and/or CDK2 kinases.
Further review and literature disclosure on protein kinase molecules have been given by Isabelle Dussault (see; Anti-Cancer Agents in Medicinal Chemistry, 2009, 9, 221-229), Ted L. Underiner et. al., (see; Anti-Cancer Agents in Medicinal Chemistry, 2010, 10, 7-27) and Stephen Claridge et. al (see; Bioorganic & Medicinal Chemistry Letters 18 (2008) 2793-2798). All of these patents and/or patent applications and literature disclosures are incorporated herein as reference in their entirety for all purposes.
Despite the advances made in the area of kinases and in particular the role that c-met, RON, EGFR or KDR pathway plays in human diseases, challenges remain in term of the complexities of the target involved, the protein structure of the kinases, specificity issues for various kinase inhibitors, side effects and desired clinical benefits expected form the small molecule inhibitors. Accordingly, there still remains an unmet and dire need for small molecule compounds having specificity towards either one, two or multiple kinase inhibitors in order to regulate and/or modulate transduction of kinases, particularly c-Met, RON, EGFR or KDR for the treatment of diseases and disorders associated with kinases-mediated events.
The c-Met pathway plays an important role in the above described human diseases including cancer. There are no c-Met inhibitors or antagonists that are currently available for treating these human disorders that are characterized by abnormal HGF/c-Met signaling. Therefore, there is a clear unmet medical need for compounds which inhibit c-Met and other kinases. The compounds, compositions, and pharmaceutical methods provided herein help meet this need.